The industrial techniques for fractionating proteins which are most used are based on a selective precipitation of the proteins by placing a solution of proteins in contact with a precipitating agent and by playing on the conditions of pH of ionic force, the nature and concentration of the precipitating agents. Among the precipitating agents which have been tested to that end, mention may be made of fatty acids comprising 6 to 14 carbon atoms and in particular caprylic acid which presents the advantage of allowing separation at ambient temperature and of being a stabilizing agent of numerous proteins.
As described in PREPARATIVE BIOCHEMISTRY, Vol. 14, No. 1, 1984, pages 1-17, Marcel Dekker, Inc.; A.F.S.A. HABEEB et al. "Preparation of human immunoglobulin by caprylic acid precipitation", a process for purification of immunoglobulins by caprylic acid plasma precipitation, followed by a step of chromatography, is already known. This process is a process of the "batch" type which means that the caprylic acid/protein ratio which enables the desired precipitation to be obtained is attained only at the end of the addition of the caprylic acid in the whole plasma batch. The caprylic acid is added with vigorous stirring which is provided by a mechanical means. The suspension obtained is centrifuged and filtered if necessary to remove the fine particles. Such a process, due to its basic conception, obviously does not lend itself to use on an industrial scale.
The present invention concerns improvements relating to such a process so as to allow it to be carried out continuously, with a high yield.